Investment Securities - Investments In Private Equity Funds Subject to Lock-Up Periods (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Debt and Equity Securities, FV-NI [Line Items]
1 – 3 years	$ 18.5
3 – 5 years	55.9
5 – 10 years	184.5
>10 years	3.1
Total	2,071.1	$ 1,998.2
Private equity funds
Debt and Equity Securities, FV-NI [Line Items]
Total	$ 262.0